EFFECT OF INTRAOPERATIVE BLOOD-LOSS ON THE SERUM LEVEL OF CEFAZOLIN IN PATIENTS MANAGED WITH TOTAL HIP-ARTHROPLASTY - A PROSPECTIVE CONTROLLED-STUDY

The effect of intraoperative blood loss on serum levels of cefazolin i n patients being managed with total hip arthroplasty was studied. Eigh teen patients, thirteen men and five women, with a mean age of sixty-f ive years (range, forty to eighty-five years) were enrolled in the stu dy. Fifteen had a primary total hip arthroplasty and three, a revision . Each patient served as his or her own control. Baseline clearance of cefazolin was determined at a minimum of forty-eight hours before the operation. Each patient received one gram of cefazolin intravenously. Serial serum concentrations were determined from specimens drawn at z ero, five, ten, twenty, thirty, sixty, 120, 240, and 300 minutes after administration. Fifteen minutes before the skin incision was made, ea ch patient again received one gram of cefazolin intravenously. Serum s amples were collected at the same time-intervals, and the serum levels of cefazolin were determined with use of capillary electrophoresis. D ata regarding intraoperative blood loss as well as replacement of flui d and blood were recorded. The administration of the antibiotic, retri eval of the serum samples, and estimation of the blood loss were perfo rmed by the same person in the same manner for all patients. The preop erative and intraoperative creatinine clearances (mean and standard de viation), estimated with use of the formula of Cockcroft and Gault, we re 62.06 +/- 21.28 and 74.02 +/- 24.75 milliliters per minute, respect ively. The amount of intraoperative blood loss averaged 1137 +/- 436 m illiliters (range, 675 to 2437 milliliters). The preoperative and intr aoperative cefazolin clearances averaged 0.49 +/- 0.21 and 0.52 +/- 0. 30 milliliter per minute per kilogram, respectively. During joint repl acement, the commonly accepted interval between doses of cefazolin is four hours. In the present study, the serum level of cefazolin at four hours was forty-five micrograms per milliliter. This corresponds to a n osseous concentration that well exceeds the minimum inhibitory conce ntration for Staphylococcus aureus, which is 0.5 microgram per millili ter. This study suggests that, with blood losses of more than 2000 mil liliters, it is not necessary to administer cefazolin at intraoperativ e intervals of less than four hours in order to maintain a concentrati on of antibiotics that is higher than the minimum inhibitory concentra tion for the most common infecting organisms.